It is known that a prosthesis implanted inside a human body can be subject to infection.
When this occurs, the infected prosthesis must be removed from the implantation site and, before implanting another prosthesis, it is necessary for the infection to be eradicated.
During such a step, spacer devices are normally used in order to keep the shape of the bone seat or of the joint seat in which the new prosthesis will be implanted substantially unchanged.
Such a procedure is known as “two-step treatment” for the removal of an infected prosthesis and the implantation of a new prosthesis.
The spacer devices typically used can have a porous outer surface, possibly impregnable with one or more pharmaceutical or medical substances to be released into the human body, at the anatomical area in which their implanting is foreseen.
In such spacer devices the amount of pharmaceutical or medical substance that can possibly be impregnated along the porous outer surface is limited by the depth and by the extension of the surface itself. In this case, the spacer device may not ensure the release of the pharmaceutical or medical substance for a period equal to that necessary for the complete healing of the infected site.
Moreover, in such a spacer device it is difficult to apply, along specific portions thereof, two or more pharmaceutical or medical substances that are different from each other while still keeping such substances separate.
There are also preformed spacer devices that are produced by casting antibiotic-loaded bone cement in a mold until it sets and extracting the set spacer device, which is then processed or finished according to requirements.
Alternatively, the surgeon can make a spacer himself during the operation, using molds, usually made from silicone of suitable geometry, which are filled with antibiotic-loaded bone cement, to which another antibiotic different from the first one is optionally added. Once polymerization has taken place, the surgeon extracts the spacer from the silicone mold, facilitated by the flexible nature of this material, and then proceeds with the implanting, possibly finishing the spacer if necessary.
Also in this case, it is difficult for a surgeon to arrange the pharmaceutical or medical substances in specific portions of the spacer device, since the antibiotic-loaded bone cement cast in the mold arranges itself freely inside it, filling its cavities.
Therefore, there is a need for the surgeon to have a spacer device, in which it is possible to add one or more pharmaceutical or medical substances along specific portions of the device, in a solution that is easy to carry out.
Moreover, there is a need to provide a spacer device that ensures the release of one or more pharmaceutical or medical substances for the entire period required to heal the infected site.
At the same time, these possibilities are associated with the need to have, in any case, a temporary and/or disposable spacer device of predetermined and correct shape and size, without the risk for the surgeon, having to make the spacer device directly in situ, to obtain a shape that is irregular or incompatible with the patient's actual anatomical requirements, or in any case to be finished and processed before implanting.